I think Jeff and Laura were told by production they had to walk into the jungle with the other group because it is much easier to film one group than two. Jeff and Laura proved they are extremely competent walking through the jungle, as they did in their initial 21 day challenge. I can't believe they suddenly felt the need for protection from others.
I also think production forced all the groups to change location from the beach to the jungle. They were doing relatively fine on the beach, and the excuse that they needed to be closer to the extraction point doesn't seem valid since they still have lots of time left.
